Durability of Float Glass and Glassceramics with Zero Thermal Expansion Coefficients

V.P. Maslov & V.E. Lashkarjov, Institute of Semiconductor Physics of HASU
Yu.M. Rodichev & Yu. N. Yevplov, G.S. Pisarenko Institute for Problems of Strength of HASU

Float glass and optical glassceramics Zerodur with zero thermal expansion coefficient are high homogeneous nano-structural elastic-brittle materials. These materials are characterized by primary influence of the surface microcrack type defects on their resistance under mechanical and thermal cyclic loading. Surface microcracks are formed at the production of basic initial glass materials and at their next processing into different products as well as under influence of operation factors. These defects may differ significantly on their shape and sizes from flat cracks which are considered usually in fracture mechanics.

Results of the investigation of regularity of short-duration and long-time bending strength of the glass and glassceramics Zerodur with taking into account the influence of typical kind and sizes of surface defects which are connected with glass production and detail surface processing technology as well as with some other factors are discussed in this paper. The parameters of kinetic diagrams of subcritical microcrack growth at this kind of brittle materials and specific geometric characteristics of the fracture focus and of the adjacent to focus part of fracture surface were analyzed after the tests of the specimens. It gave a possibility using the linear fracture mechanics theory to make calculating evaluations of the strength and durability of structure elements. The results correlated satisfactorily with received testing data for specimen durability up to three months.

Some peculiarities of subcritical fracture of the investigated materials with amorphous and glass-crystalline structures on the mechanism of "static fatigue" under mechanical and thermal cyclic loading were established. It was shown that curve of long-time strength for both type materials are characterized by parameter n ~ 20…24 and extent of decreasing of theirs bending strength at the increasing of loading durability is practically equal. This result shows on the primary influence of amorphous matrix mechanical properties on glassceramics Zerodur durability.

Results received in this work may be used to raise the strength and durability of glass and glassceramics structures by the way of optimization of their production technology, mechanical processing and design methods as well as thanks to using the means of the detail surface protection from mechanical damages and from influence of environment at the operation.

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The Authors

Dr. Yurii Rodichev Dr. Head of the Department G.S.Pisarenko Institute for Problems of Strength of NASU Scientist and specialist on glass and ceramics constructional strength. Design and testing of glass and ceramics structures for different spheres of technics. Dr. Yurii Rodichev is the Head of the ... Read more